Recently, two electronic apparatuses are often used while being connected to each other. For example, a table computer (hereinafter referred to as a tablet) is often connected to a keyboard. Various applications can be activated on the tablet and various buttons on an interface screen of the applications can be selected by touch operations. Of course, a software keyboard can be displayed on the screen of the tablet and characters can be input by touching the keyboard. However, some users prefer to input characters by means of a physical keyboard. Therefore, keyboard docks are sold separately. A keyboard dock includes a connector to which a tablet is connected, and a mechanism which maintains the state of the tablet connected to the connector. If the tablet is secured to the keyboard dock, the tablet can be used like a note PC.
In order to use the tablet by connecting the tablet to the keyboard dock, a connection between the tablet and the keyboard dock should be detected. The connection is generally detected by transmitting a signal for confirmation of connection from one apparatus to the other apparatus via a specific terminal.